Editing T (programming language)

{{Short description|Dialect of the Scheme programming language}}
{{Infobox programming language
| name = T
| logo = 
| paradigms = [[Multi-paradigm programming language|Multi-paradigm]]: [[Object-oriented programming|object-oriented]], [[Imperative programming|imperative]], [[Functional programming|functional]], [[Metaprogramming|meta]]
| family = [[Lisp (programming language)|Lisp]]
| designers = Jonathan A. Rees<br/>Norman I. Adams
| developers = same
| released = {{Start date and age|1982}}
| latest release version = 3.0
| latest release date = {{Start date and age|1984|08|01}}
| typing = [[dynamic typing|dynamic]], [[Strong and weak typing|strong]]
| scope = 
| programming language = 
| discontinued = Yes
| platform = Cross-platform
| operating system = [[Cross-platform software|Cross-platform]]
| license = 
| file ext = 
| file format = <!-- or: | file formats = -->
| website = {{URL|mumble.net/~jar/tproject}}
| implementations = 
| dialects = 
| influenced by = [[Scheme (programming language)|Scheme]]
| influenced = [[EuLisp]], [[Joule (programming language)|Joule]]
}}

'''T''' is a [[Dialect (computing)|dialect]] of the [[Scheme (programming language)|Scheme]] [[programming language]] developed in the early 1980s by Jonathan A. Rees, [[Kent Pitman|Kent M. Pitman]], and Norman I. Adams of [[Yale University]] as an experiment in language design and implementation.<ref>{{cite book |last1=Slade |first1=Stephen |year=1987 |title=The T programming language: a dialect of LISP |publisher=Prentice-Hall |publication-place=Englewood Cliffs, New Jersey |isbn=978-0-13-881905-7 |oclc=16094677}}</ref>

==Rationale==
T's purpose is to test the thesis developed by [[Guy L. Steele Jr.]] and [[Gerald Jay Sussman]] in their series of papers about Scheme: that Scheme may be used as the basis for a practical programming language of exceptional expressive power, and that implementations of Scheme could perform better than other Lisp systems, and competitively with implementations of programming languages, such as [[C (programming language)|C]] and [[BLISS]], which are usually considered to be inherently more efficient than Lisp on conventional machine architectures. Much of this occurs via an [[optimizing compiler]] named Orbit.

T contains some features that modern Scheme lacks. For example, T is [[Object-oriented programming|object-oriented]], and it has first-class environments, called ''locales'', which can be modified non-locally and used as a module system. T has several extra special forms for [[lazy evaluation]] and [[Control flow|flow control]], and an equivalent to [[Common Lisp]]'s [[setf (disambiguation)|setf]]. T, like Scheme, supports [[call-with-current-continuation]] (call/cc), but it also has a more limited form called <code>catch</code>. From the T manual, a hypothetical implementation of <code>[[cons]]</code> could be:

<syntaxhighlight lang="scheme">
 (define-predicate pair?)
 (define-settable-operation (car pair))
 (define-settable-operation (cdr pair))
 (define (cons the-car the-cdr)
         (object nil
                 ((pair? self) t)
                 ((car self) the-car)
                 ((cdr self) the-cdr)
                 (((setter car) self new-car) (set the-car new-car))
                 (((setter cdr) self new-cdr) (set the-cdr new-cdr))))
</syntaxhighlight>

This example shows that objects in T are intimately related to closures and message-passing. A primitive called <code>join</code> puts two objects together, allowing for something resembling [[Inheritance (object-oriented programming)|inheritance]].

{{Lisp}}

==Ports==
T was ported to many hardware [[Computing platform|platforms]] and [[operating system]]s, including:<ref>{{cite web |url=http://mumble.net/~campbell/t/t.html |title=T Revival Project |last=Campbell |first=Taylor `Riastradh' |date=7 April 2006 |website=Mumble.net |publisher=Internet Archive Wayback Machine |archive-url=https://web.archive.org/web/20070103020434/http://mumble.net/~campbell/t/t.html |archive-date=2007-01-03 |access-date=2018-11-18 |url-status=live }}</ref>

*[[MIPS architecture|MIPS]]: DEC 3100 (pmax), [[SGI IRIS]]
*[[Motorola 68000]] (m68k): Apollo Domain/OS, [[HP/UX]], Mac/AUX, [[NeXT]], [[SunOS]] 3
*[[NS320xx]] (n32k): [[Encore Computer|Encore]] Multimax
*[[SPARC]]: SunOS 4 and above, [[Solaris (operating system)|Solaris]], [[Unix]] on [[Connection Machine]] 5
*[[VAX]]: Ultrix

==See also==
{{Portal|Computer programming}}

==References==
{{Reflist}}

==External links==
* {{Official website|mumble.net/~jar/tproject}}
* [http://www.paulgraham.com/thist.html History of T], by Olin Shivers
* [https://web.archive.org/web/20170515045004/http://repository.readscheme.org/ftp/papers/t_manual.pdf T manual] (PDF) from ReadScheme, via the Internet Archive

{{Lisp programming language}}
{{Authority control}}

[[Category:Lisp programming language family]]
[[Category:Scheme (programming language)]]
[[Category:Programming languages created in 1982]]
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[[Category:Articles with example Lisp (programming language) code]]